Tropical Storm Fiona Forecast Discussion Number 10

By | September 16, 2022

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WTNT42 KNHC 162049
TCDAT2

Tropical Storm Fiona Discussion Number  10
NWS National Hurricane Center Miami FL       AL072022
500 PM AST Fri Sep 16 2022

The bulk of the Fiona's convective activity remains sheared to the
east of the center.  However, there are some initial signs of new
convection developing in a small ring around the center, the
low-level cloud field is thickening up a bit, and visible satellite
images show high-level convective cirrus blowing from east to west.
It remains to be seen if this is suggestive of some lessening of the
deep-layer shear over the system and a moistening of the ambient
atmosphere.  The initial intensity remains 45 kt given little change
in Fiona's organization since earlier today.  The next Air Force
Reserve reconnaissance mission is scheduled for this evening.

Fiona's center jumped a bit to the north today, and it's just
about to move over or just to the north of Guadeloupe.  The initial
motion is estimated to be 280 degrees at 13 kt, with the storm
being steered westward by subtropical ridging to the north.  The
track forecast philosophy has not changed from earlier today.
Fiona is expected to reach the western edge of the ridge, slow
down, and turn northwestward by day 3, and then north-northwestward
by day 5.  The guidance remains in generally good agreement on this
scenario, with the notable exception being the ECMWF model, which
shows a smaller Fiona not turning as sharply or moving as fast as
in the other models by the end of the forecast period.  The new NHC
track prediction is adjusted northward during the first 48-60 hours
of the forecast to account for the northward jump of the center,
but it otherwise falls back in line with this morning's forecast on
days 3 through 5 and lies a bit to the west of the consensus aids.

Assuming that recent satellite trends are a harbinger of possible
strengthening, the NHC intensity forecast continues to show gradual
intensification while Fiona moves across the far northeastern
Caribbean Sea during the next 48 hours.  Although Hispaniola's
terrain could cause some weakening in the 60-72 hour period, the
amount of weakening will probably depend on how much of the wind
field moves over the island or remains over the adjacent waters.
After 72 hours, the global models indicate that the circulation
will become re-established over the far southwestern Atlantic, and
the official forecast continues to show Fiona becoming a
hurricane by the end of the forecast period.


Key Messages:

1. Tropical storm conditions are beginning to spread across the
Leeward Islands and will continue through Saturday morning.
Tropical storm conditions will spread westward across the U.S. and
British Virgin Islands on Saturday and Puerto Rico late Saturday
and Saturday night.  Tropical storm conditions are possible over
Dominica tonight and within the watch area in the Dominican
Republic on Sunday.

2. Heavy rains from Fiona will reach the Leeward Islands by this
evening, spreading to the British and U.S. Virgin Islands and Puerto
Rico Saturday, reaching the Dominican Republic Sunday, and Haiti
and the Turks and Caicos Monday through Tuesday.  This rainfall
may produce considerable flood impacts including flash and urban
flooding, along with mudslides in areas of higher terrain.

3. Fiona is expected to strengthen gradually over the northeastern
Caribbean Sea, and it could be near hurricane strength as it
approaches the southern or eastern coast of the Dominican Republic
Sunday afternoon.  Warnings could be required for portions of
the Dominican Republic tonight or on Saturday.

4. Fiona is forecast to strengthen after moving across Hispaniola
early next week, and interests in the Turks and Caicos Islands and
southeastern Bahamas should continue to monitor forecasts for the
storm.


FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 16.4N  61.1W   45 KT  50 MPH
 12H  17/0600Z 16.8N  62.8W   50 KT  60 MPH
 24H  17/1800Z 17.2N  64.9W   50 KT  60 MPH
 36H  18/0600Z 17.6N  66.6W   55 KT  65 MPH
 48H  18/1800Z 18.2N  68.2W   60 KT  70 MPH
 60H  19/0600Z 18.8N  69.2W   55 KT  65 MPH...OVER DOM. REPUBLIC
 72H  19/1800Z 19.6N  70.2W   55 KT  65 MPH...OVER DOM. REPUBLIC
 96H  20/1800Z 21.6N  71.7W   60 KT  70 MPH...OVER WATER
120H  21/1800Z 23.6N  72.2W   70 KT  80 MPH

$$
Forecaster Berg

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